Base class for components using native code ( libjkjni.so ).
It allows to access the jk_env and wrap ( 'box' ? ) a native
jk component, and call it's methods.
Note that get/setAttribute are expensive ( Strings, etc ),
invoke() is were all optimizations are done. We do recycle
all memory on both C and java sides ( the only exception is
when we attempt pinning but the VM doesn't support it ). The
low level optimizations from ByteBuffer, etc are used to
reduce the overhead of passing strings.